In 2017 two theoretical groups, Liu et al.,[1]}, [2]} and Peng et al.,[3]} nearly simultaneously predicted \({\cal M}\) H\(_{10}\) , with isovalent \({\cal M}\) =La and Y, to have high T\(_c\) , in the 275-325K range depending on element and pressure (always above 200 GPa). Liu et al. calculated \(\lambda =2.2\) , with T\(_c\)  around 265K. The structure again was the highest symmetry possible for this stoichiometry, cubic with a clathrate-like shell of 32 H atoms surrounding the metal atom on its fcc sublattice, pictured in Fig. REF (c). Values for \(\lambda \)  were in the 2.2-2.6 range, similar to SH\(_3\)  but also similar to Pb-Bi-Tl alloys from the 1970s with maximum T\(_c\) =9K that is 35 times lower.[4]} The differences in T\(_c\)  are due to the very high H vibrational frequencies (Ashcroft's primary point) while retaining strong coupling to Fermi surface electrons. Further studies of this superconductivity were provided by Liu et al.[5]} and the quantum (zero point motion) nature of the structure by Errea et al.[6]}
Theoretical work by Ge et al.[7]} indicates that doping LaH\(_{10}\)  by B or N at the few percent level might raise T\(_c\)  by 30K, i.e. to T\(_c\approx \) 290K, in the 240 GPa regime.
